2 Geography and ScienceFigure 1-1: The elements of geography can be grouped into 2 broad categories. Physical geography primarily involves the study of natural science, whereas cultural geography primarily entails the study of social science.
3 Geography and Science The scientific method Scientific “proof” Observe phenomenaFormulate a hypothesisDesign an experiment to test the hypothesisPredict the outcome of the experimentConduct the experimentDraw conclusionsScientific “proof”Establishment of scientific theory
4 Earth Systems Closed systems – those contained from outside influence Open – energy & matter free to be exchanged across systemsEquilibrium – systems are in balance (input = output)Interconnected systems – change in one system affects anotherFeedback loops, positive versus negativeFigure 1-6: A simplified view of a glacier as an open system. The primary material inputs of a glacier include show, ice, and rock, whereas its outputs include meltwater, water vapor, and rock transported by the flowing ice. The energy interchange includes incoming solar radiation and the exchange of latent heat between ice, liquid water, and water vapor.
5 Earth and the Solar System Origins – the big bangFormation of the solar systemThe Milky WayFormed 4.5 to 5 billion years agoFigure 1-7: The structure of the Milky Way Galaxy showing the approximate location of our Sun on one of the spiral arms.Figure 1-8: The birth of our solar system. (1) diffuse gas cloud, or nebula, begins to contract inward. (2) Cloud flattens into nebular disk as it spins faster around a central axis. (3) Particles in the outer parts of the disk collide with each other to form protoplanets. (4) Protoplanets coalesce into planets and settle into orbits around the hot center. (5) The final product: a central Sun surrounded by eight orbiting planets. The original nebular disk was much larger than our final solar system.
6 Earth and the Solar System Formation of the solar systemEight planets revolve around the Sun in elliptical orbitsFour terrestrial planetsFour gas giantsEarth is the third planetFigure 1-9: The solar system. The Sun is not exactly at the center of the solar system – the planets revolve around the Sun in elliptical orbits. The Kuiper Belt, which includes dwarf planets such as Pluto, begins beyond Neptune.
7 Earth’s Physical Characteristics Maximum reliefFigure 1-10: Earth is large relative to the size of its surface features. Earth’s maximum relief (the difference in elevation between the highest and lowest points) is 19,883 meters (65,233 feet) or about 20 kilometers (12 miles) from the top of Mount Everest to the bottom of the Mariana Trench in the Pacific Ocean.
8 Earth’s Physical Characteristics Imperfect sphereEquatorial diameter ~ 12,756 kmPolar diameter ~ 12,714 kmCircumference of 40,000 kmFigure 1-11: Earth is not quite a perfect sphere. It’s surface flattens slightly at the North Pole and the South Pole and bulges our slightly around the equator. Thus, a cross section through the poles, shown in (a), has a diameter slightly less than the diameter through the equator, shown in (b).
9 The Geographic Grid – Latitude and Longitude Location on EarthNeed an accurate location on Earth to describe geographic featuresUse Earth’s rotation axis to base location on the surfaceNorth Pole and South PolePlane of the equatorFigure 1-12: An example of a grid system. The location of point X can be described as 2B or B2; the location of Y is 3D or D3.Figure 1-13: Earth spins around its rotation axis, an imaginary line that passes through the North Pole and the South Pole. An imaginary plane bisecting Earth midway between the 2 poles defines the equator.
10 Great CirclesCircles that bisect a sphere and pass through the sphere’s centerIdentify the shortest distance between two points on a sphere—great circle distancePlane of the equator is a great circleSmall circlesFig 1-14: Comparison of great and small circles. (a) A Great circle results from the intersection of Earth’s surface with any plane that passes through Earth’s center. (b) A small circle results from the intersection of Earth’s surface with any plane that does not pass through Earth’s center.
11 The Geographic Grid – Latitude GraticuleLatitudesAngle north or south of the equatorParallelsFig 1-15: Measuring latitude. An imaginary line from Kuji, Japan, to Earth’s center makes an angle of 40 with the equator. Therefore, Kuji’s latitude is 40° N. An imaginary line from Bowen, Australia, to Earth’s center makes an angle of 20, giving this city a latitude of 20° S.Fig 1-16: Lines of latitude indicate north-south location. They are called parallels because they are always parallel to each other.
12 Seven Important Latitudes Latitude zonesFigure 1-17: Seven important parallels. As we will see when we discuss the seasons, these latitudes represent special locations where rays from the Sun strike Earth’s surface on certain days of the year.Figure 1-18: The tropic of Capricorn; like all other parallels of latitude, is an imaginary line. As a significant parallels, however, its location is often commemorated by a sign.
13 The Geographic Grid –Longitude LongitudesAngular description of east–west directionMeridiansFigure 1-19: Lines of longitude, or meridians, indicate east-west and all converge at the poles.Figure 1-21: The meridians that mark longitude are defined by intersecting imaginary planes passing through the poles. Shown hear are the planes for the prime meridian through Greenwich, England, and the meridian through Freetown, Sierra Leone, at 13° W longitude.
14 Important Longitudes Longitudes Important longitudes Convergence at polesFigure 1-20: The prime meridian of the world, longitude 0° at Greenwich, England, which is about 8 km (5 miles) from the heart of London.Figure 1-22: A polar view of meridians radiating from the North Pole. Think of each line as the top edge of an imaginary plane passing through both poles. All the planes are perpendicular to the plane of the page.
15 Graticule Location on the graticule based on latitude and longitude Figure 1-23: The complete grid system of latitude and longitude – the graticule. Because the meridians converge at the poles, the distance of 1° of longitude is greatest at the equator and diminishes to zero at the poles, whereas the distance of 1° of latitude varies only slightly (due to the slight flattening of Earth at the poles).